December 1, 1996
Various methods have been utilized to decontaminate citrus leaves prior to analyzing for nutritional status. Sources of contamination can be dust or dirt particles and chemical sprays which have been applied to the citrus tree. Valencia orange (Citrus sinensis L.) trees were sprayed with zinc oxide at 5 lb Zn/acre and basic zinc sulfate at 2.5 and 5 lb Zn/ acre rates. After the trees were sprayed, leaves were analyzed 7 and 28 days after treatment (DAT) to compare 6 wash treatments for effective removal of Zn from external leaf surfaces. At 42 days after treatment, one of the 6 hand-wash methods was compared to a jar wash treatment. Detergent plus HCl acid wash or washes containing EDTA were effective in removal of Zn nutritionals. These wash treatments were also most effective in removal of all nutrients contaminating the leaf surfaces. A jar wash was equally effective in removal of surface material as compared to hand washing and is easier and quicker. Leaf absorption of basic Zn sulfate at 2.5 lb Zn/acre or 5 lb Zn/acre was equal to Zn oxide at 5 lb Zn/acre for the 7 and 28 days after treatment. However, by 42 days after spraying the leaves, the Zn oxide treatment was superior for Zn absorption. Large amounts of rainfall and the almost complete solubility of basic Zn sulfate appears to have aided in washing the compound off the leaves. This was likely the cause for the lower absorption of Zn from this nutritional source than was expected.